1. Field of the Invention:
This invention generally concerns a method for controlling an internal combustion four-stroke engine and more particularly concerns a method for independently controlling combustion chamber inlet and outlet devices by variable synchronization of the opening and closing duration times of the inlet and outlet devices.
2. Description of the Prior Art:
Adaptable control of the inflow and outflow of the work medium in internal combustion engines is desired in order to optimally influence the combustion process according to any operating conditions associated with such engines. Such adaptable or variable control is particularly desirable in intermittent internal combustion engines, as such engines operate under widely varying operating conditions.
Camshafts usually are used to control the gas shuttle valves, slide valves, etc. in internal combustion engines. Systems of this type have the disadvantage that they have little or no influence on the opening and closing valve timing durations.
According to the present state of the art, in reciprocating piston internal combustion engines such as Otto engines in which the fuel-air mixing ratio must be maintained within certain narrow limits, the engine load must be controlled by controlling the amount of fresh air and fuel mixture in the work chamber. The usually invariable valve duration control times which result from the cam shape of a camshaft necessitates the amount of fresh air and fuel mixture to be controlled by throttling the inlet system. This throttling produces gas exchange losses and unfavorable amounts of residual gas in the cylinder charge.
It has been suggested that the disadvantages of throttling can be avoided by varying the control timing of the inlet opening. Thus, for example, SAE paper 770,880 by Sherman and Blumberg suggests that an engine load control can be achieved by metering the air-fuel charge into the work chamber with a variable inlet control time. This adaptation of the inlet control constitutes an improvement over an inflexible inlet control, because the usual throttle device and the losses associated with it can be eliminated. However, such type of load control also entails disadvantages. Specifically, as the load decreases, the effective compression ratio drops and the compression temperature decreases. This causes the ignitability of the mixture and the quality of the combustion to drop. Thus, the advantages of eliminating throttle losses are partially or entirely cancelled out in the instance of an engine under partial load.